Revisable Anterior Cervical Plating System

ABSTRACT

An improved anterior cervical plating system and methods of cervical fusion using such a system are provided. The cervical plating system includes an interlocking mechanism that integrated into each of the plates such that any two plates may cooperatively engage through the interlocking mechanism such that a new cervical plate can be interconnected with a pre-existing plate during revision surgery without removal of the pre-existing plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The current application is a continuation application of U.S. patentapplication Ser. No. 15/090,327 filed Apr. 4, 2016, which applicationwas a continuation of U.S. patent application Ser. No. 14/752473 filedJun. 26, 2015, which application was a continuation of U.S. patentapplication Ser. No. 14/481208 filed Sep. 9, 2014 (now U.S. Pat. No.9,095,381), which application was a continuation of U.S. patentapplication Ser. No. 14/028282 filed Sep. 16, 2013 (now U.S. Pat. No.8,858,556), which application was a continuation of U.S. patentapplication Ser. No. 13/281603 filed Oct. 26, 2011 (now U.S. Pat. No.8,556,895), which application was a continuation of U.S. patentapplication Ser. No. 11/453440 filed Jun. 14, 2006 (now U.S. Pat. No.8,070,749), which application was a continuation-in-part of U.S. patentapplication Ser. No. 11/417794, filed May 3, 2006 (now abandoned), whichitself claimed priority to U.S. Provisional Patent Application No.60/680728, filed May 12, 2005, the disclosures of which are incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The current invention is related to an improved anterior cervicalplating system; and particularly to a new method of interconnectinganterior cervical plates.

BACKGROUND OF THE INVENTION

Anterior cervical plating systems are well known, and there are a numberof different such systems on the market. All currently available platingsystems use a metal, usually titanium although any suitable surgicalmaterial may be used, plate, screws which go through the plate into thevertebra, and a locking mechanism, whereby the screw is locked to theplate. Locking is accomplished by a variety of mechanisms; a CSLP (asmaller central screw expands the head of the bone screw to lock it intothe plate), a lock washer or press fit which locks the screw into theplate, or a locking device attached to the plate which is applied to thescrew after it has been tightened. These designs include cams, washers,plates and screw-on caps applied to the plate after the screw has beenengaged. Initial plate designs were rigid, but this led to the conceptof stress shielding, and it was felt that rigid plates prevent loadsfrom being transmitted through bone grafts, which can interfere withfusion and allow for grafts to be reabsorbed.

Although a substantial number of different plate designs have beendeveloped, few of these systems adequately address a difficult surgicalproblem, revision surgery. Revision surgery is required in a patient whohas already had an anterior cervical fusion, and who develops adjacentlevel disease. With current anterior cervical plating systems it isnecessary to remove the previous plate in order to operate on theadditional level. If a patient has had multiple levels done, the priorplate must come off of all of the previous levels in order to plate thepreviously unoperated adjacent level This is difficult surgically, andis associated with increased operative morbidity.

Accordingly, a need exists for an improved anterior cervical platingsystem with improved interconnectivity such that revision surgery isless intensive and traumatic to the patient.

SUMMARY OF THE INVENTION

The current invention is directed to an improved anterior cervical platethat allows a new plate to be attached to the prior plate, so that theold plate does not have to be removed.

In one embodiment, the anterior cervical plating system of the currentinvention includes a pre-positioned cervical plate having vertebralanchoring means and at least one base interlocking portion integratedtherein. In such an embodiment the base interlocking portion is designedto engage a revision cervical plate, the revision cervical plates havingits own vertebral anchoring means, an additional integrated baseinterlocking portion and an additional integrated cooperativeinterlocking portion. Regardless of the actual design of theinterlocking portions, each of the base interlocking portions isdesigned to cooperatively engage each of the cooperative interlockingportions to provide a stabilizing interconnection between two adjacentplates, the stabilizing interconnection being capable of resistingmovement of the adjacent cervical plates in at least one dimension, andwherein the operation of said stabilizing interconnection is independentof the operation of the vertebral anchoring means.

In another embodiment the system of the current invention uses at leastone vertebral screw as the vertebral anchoring means.

In still another embodiment, the system of the current invention uses achannel integrally formed into at least one of the distal or proximalend of each of the cervical plates as the base interlocking portion. Insuch an embodiment, the cooperative interlocking portion comprises anarmature interlockingly cooperative with the channel.

In yet another embodiment, the system of the current invention, thechannel and the armature further include a pair of cooperative groovesand that interlock to prevent movement of the armature relative to thechannel in at least one dimension. In such an embodiment, the groovesmay be disposed in any confirmation, such as longitudinally along atleast a portion of the sides of the armature and the channel, oralternatively, along at least a portion of the opposing faces of thearmature and the channel.

In still yet another embodiment, the system of the grooves may furtherinclude at least one barb formed therein such that when the armature isdrawn past the barb, said barb prevents further movement of the armaturein at least one direction along said groove.

In still yet another embodiment, the armature may attach into thechannel from any direction including either parallel or perpendicular tothe longitudinal axis of the channel.

In still yet another embodiment, the armature and the channel aredesigned to cooperatively taper such that when the armature is drawnlongitudinally away from the center of the channel the tapers interlockto prevent motion of the armature relative to the channel in at leastone dimension. In such an embodiment, the channel is bidirectional thattapers both proximally and distally from the center of the plate.

In still yet another embodiment, the channel and armature furtherinclude a series of cooperative teeth formed crosswise across at least aportion of the opposing faces of the channel and armature.

In still yet another embodiment, the armature is formed by two parallelrails separated by a gap. In such an embodiment, the rails may bedynamically inwardly deformable. In still yet another such embodiment,the channel may further include a locking screw positioned to fit withinthe gap between the rails of the armature such that when tightened thelocking screw locks the armature into the channel to prevent movement ofthe armature relative to the channel.

In still yet another embodiment, the armature interlocks with thechannel by at least partially engaging the outer surface of the plate.In such an embodiment, the channel and armature may be interlockingmirror images. In still yet another such embodiment, the revision plateis attached to the original plate through a separate anchoring screwsuch that the vertebral screws on the original plate are left in place.

In still yet another embodiment, an external gripping plate may bedesigned to allow for an angular adjustment to the axis of the revisionplate.

In still yet another embodiment, the cervical plates use a maximum oftwo vertebral anchoring means and cervical plate shares at least onevertebral anchoring means with an adjacent plate. In such an embodiment,the shared vertebral anchoring means may be disposed to engage both thearmature and the channel of the adjacent plates. In still yet anothersuch embodiment the channel may be formed with at least one externalsurface of the cervical plate and the armature has a cooperative grooveand is formed to engage the external surface of adjacent cervical plate.

In still yet another embodiment, the revision plate may include at leasttwo additional independent vertebral anchoring means.

In still yet another embodiment, the armature and channel are formed onthe opposing lateral faces of the adjacent cervical plates and buttressagainst each other. In such an embodiment, the armature and channel maybe formed in any suitable form including as a set of cooperativegrooves, as a pair of cooperative stepped surfaces, and as a pair ofinterference fit surfaces, for example.

In still yet another embodiment, the armature and channel may be linkedby a separate flexible band of material.

In still yet another embodiment, the cervical plates further include aremovable cap for protectively covering base interlocking portion of thecervical plate when the base interlocking portion is unengaged with acorresponding cooperative interlocking portion.

In still yet another embodiment, the cervical plates further include anopening formed in the body of the plate disposed such that the openingoverlaps and allows visual inspection of the disc space between twoadjacent vertebra when said cervical plate is anchored in position.

In still yet another embodiment, the system further includes adistraction device designed to interlock with the integrated baseinterlocking portion of a cervical plate

In still yet another embodiment, the invention is directed to a methodof performing an anterior cervical fusion utilizing the inventiveanterior cervical plating system.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings, which areshown in schematic form, wherein:

FIGS. 1a to 1f are directed to a first embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 2a to 2h are directed to a second embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 3a to 3e are directed to a third embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 4a to 4e are directed to a fourth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 5a to 5f are directed to a fifth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 6a to 6e are directed to a sixth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 7a to 7f are directed to a seventh embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 8a to 8d are directed to an eighth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 9a to 9c are directed to a ninth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 10a to 10c are directed to an alternative embodiment of theembodiment of the anterior cervical plating system in accordance to thecurrent invention provided in FIG. 9.

FIGS. 11a to 11c are directed to an alternative embodiment of theembodiment of the anterior cervical plating system in accordance to thecurrent invention provided in FIG. 9.

FIGS. 12a to 12c are directed to an alternative embodiment of theembodiment of the anterior cervical plating system in accordance to thecurrent invention provided in FIG. 9.

FIGS. 13a to 13g are directed to an alternative embodiment of theembodiment of the anterior cervical plating system in accordance to thecurrent invention provided in FIG. 9.

FIGS. 14a to 14f are directed to an alternative embodiment of theembodiment of the anterior cervical plating system in accordance to thecurrent invention provided in FIG. 9.

FIG. 15 is directed to an alternative embodiment of the embodiment ofthe anterior cervical plating system in accordance to the currentinvention provided in FIG. 9.

FIGS. 16a to 16c are directed to an alternative embodiment of theembodiment of the anterior cervical plating system in accordance to thecurrent invention provided in FIG. 9.

FIGS. 17a and 17b are directed to a tenth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 18a to 18e are directed to a eleventh embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 19a and 19b are directed to an twelfth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 20a to 20c are directed to a thirteenth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 21a to 21c are directed to a fourteenth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 22a to 22c are directed to a fifteenth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 23a and 23b are directed to a sixteenth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 24a and 24b are directed to a seventeenth embodiment of ananterior cervical plating system according to the current invention.

FIGS. 25a to 25g are directed to a eighteenth embodiment of an anteriorcervical plating system according to the current invention.

FIGS. 26a to 26d are directed to an embodiment of a distraction systemfor use with an anterior cervical plating system according to thecurrent invention.

DETAILED DESCRIPTION OF THE INVENTION

The current invention is directed to an improved revisable anteriorcervical plate system that allows for a new plate to be attached andintegrated into the prior plate, such that the old plate does not haveto be removed during a revision surgery.

Although the figures and following discussion will provide a detaileddescription of a number of exemplary embodiments of the cervical platesystem of the current invention, it should be understood that any numberof designs can be used to achieve the basic goal of the system. Forexample, in their basic form each of the exemplary plating systemsinclude an existing plate and a revision plate each designed to beanchored to a vertebral bone through a vertebral anchoring means, suchas, a connecting screw. A characteristic feature of this plate system isthat each of the revision plates includes an interlocking portion thatprovides a linkage between the plates. The linkage can be eitherflexible or rigid, of any suitable design such that the two plates canbe lockingly connected without removal of the existing plate. Theselinkages in turn can be locked rigidly between the plates (in aso-called fixed system), or can be allowed to travel to a limited degreeto allow for settling (in a so-called dynamic system). The choice ofwhether to use a fixed or dynamic system is left to the surgeon.

In addition, it should be understood that the figures are merelyschematic, and that the relative dimensions of the various elements andtheir relative spacings are merely exemplary and could be varied by oneof ordinary skill in the art while remaining within the bounds of thisdisclosure. For example, the size and spacing of the vertebral anchoringmeans (e.g., the vertebral screws), as well as the placement and sizingof the interlocking mechanism could be varied such that more substantialscrews with more limited spacing there between could be used. Likewise,the overall shape and dimensions of the plates could be altered to allowthe revision system of the current invention to conform with anycurrently available cervical plating system.

Regardless of the ultimate design, both the original and the revisionplates of the current invention are constructed as an integrated platesystem such that the interlocking portion of the revision platecooperates with the base interlocking portion of the original plate.These interlocking portions have coordinating surfaces that lock the twoplates together and provide torsional stability to and between theplates in at least one dimension that is independent of the connectingscrews.

Several variants of this basic design are shown in FIGS. 1 to 25, all ofwhich incorporate the basic innovation of having a linkage system thatboth allows a new plate to be securely fixed to a preexisting plate andhas coordinating surfaces between the old and new plates that whencombined provide stability to and between the plates independent of thevertebral connecting screws.

In one example these interlocking portions (linkages and coordinatingsurfaces) take the form of a dovetail slider. A dovetail slider can beformed in a number of different ways and roughly resembles acabinet-style joinery. In FIGS. 1a to 1f an embodiment of a stackablecervical plating system of the current invention having a simple grooveand joint dovetail slider system is shown. In this embodiment, as shownin FIGS. 1a to 1d , the pre-installed plate (10), which has previouslybeen affixed to the anterior cervical spine has a groove (12) runningbetween two mounting screws (14), and the new plate (16) has acorresponding linkage arm (18), which inserts into the groove (12) ofthe old plate (10) between the two screws (14). Top-views (FIGS. 1a and1b ), a cross-sectional view (FIG. 1c ), and a profile view (FIG. 1d )of these exemplary plates are provided. As shown by the cross-sectionalview provided in FIG. 1c , the groove is cut such that the linkage canonly move in a single dimension along the longitudinal axis of theoriginal plate thereby providing stability to and between the plates inall other flexural directions.

In addition to this inherent stability provided by the linkage/groovedesign, as shown in FIGS. 1a and 1b , the screws (14) overlap the groove(12) of the old plate (10). As a result of this geometry, once the arm(18) of the new plate (16) has been inserted into the groove of the oldplate, the new plate can either be locked into a fixed position bytightening the overlap screws, or the screws can be left loose to allowthe new plate to settle providing a dynamic plate system. Schematicdiagrams of this embodiment of the invention installed on the spine of apatient are further provided in FIGS. 1e and 1f . Although similar viewsare not provided for each of the remaining exemplary plate systems, itshould be understood that their installation on a patient would beidentical.

In addition, as shown in FIGS. 1a, 1b, and 1d , an optional window (20)can be provided in the plate system to allow for the inspection of thedisc space. Such a window is particularly valuable to observe anybone-graft material that might have been disposed within the spacebeneath the plate system.

In the above-embodiment, as well is in the embodiments that follow, itshould be understood that the grooves and window cut-outs on the platescan optionally be provided with snap-in pieces that fill the grooves andcut-outs of the plates until such time as a new plate is needed. Such afiller piece would be advantageous to prevent the accumulation of boneor other organic matter within the groove or cut-out of the plate thatmight foul the working elements of the plate and prevent a successfulinterlock between the plates.

FIGS. 2a to 2h demonstrate an alternative embodiment of the basicdovetail configuration. As shown in FIGS. 2a and 2b , the old plate (22)has a grooved channel (24), which corresponds to a cooperative groove(26) on the interlock arm (28) of the new plate (30), such that whenengaged by the new plate the grooved upper edge (24) of the old plateoverlaps the cooperative groove (26) of the arm (28) of the new plate toprovide a secure connection between the two plates. This groove andoverlap mechanism allows the arm (28) of the new plate (30) to snap intoposition from and then to lock (as shown in FIGS. 2c to 2f ) so that itmay be positioned from above and does not have to be fed in parallel tothe previously placed plate (22), as in the embodiment shown in FIG. 1.FIGS. 2g and 2h provide detailed cross-sectional diagrams of the groovedchannel (24) of the old plate and arm (28) of the new plate,respectively.

Again, as discussed above, the interlocking grooves on the channel ofthe old plate and the arm of the new plate provide a linkage whenengaged that can only be moved in a single dimension distally along thelongitudinal axis of the original plate thereby providing stability toand between the plates in all other flexural directions. Although onlysimple groove profiles are shown in this embodiment, it should beunderstood that any groove profile suitable for interlocking the arm ofthe new plate with the old plate may be utilized. For example, a groovewith a locking barb may also be used, which would allow for a lockingsnap fit of the new plate. In addition, as shown in all of the figures,this plate may also be equipped with a window (32) for the inspection ofthe disc space.

Collectively, FIGS. 3a to 3e depict another exemplary embodiment of thedovetail slider system in which the dovetail (as shown in FIG. 3a ) istapered to form a trapezoidal groove or channel (40) on thepre-installed plate (42) and an interlocking trapezoidal arm (44) on thenew plate (46). Such a trapezoidal geometry again allows for the newplate to be moved into the groove from above and the locked intoposition (as shown in FIGS. 3b and 3c ). In addition, the trapezoidalshape and the cooperative groove both operate together to provide alinkage that can only move in a single dimension distally along thelongitudinal axis of the original plate thereby providing stability toand between the plates in all other flexural directions. Again althoughonly standard grooves are shown in these embodiments, it should beunderstood that these linkages could also be provided with lockinggrooves to positively lock the arm of the new plate into position withinthe trapezoidal channel of the old plate.

FIGS. 3a to 3c , show only a single directional plate system, in whichthe trapezoidal window (40) only runs in one direction along thepre-installed plate, allowing for the addition of a new plate only onthe side (or one level) of the pre-installed plate with the groove.However, as shown in FIGS. 3d and 3e , added flexibility can be achieveby providing a bidirectional channel (48) on the pre-installed plate.Such a bidirectional channel would allow for the addition of new plateson both adjacent levels of the spine.

As discussed above, the channel (40) within which the arm (44) of thenew plate (46) rests can also be provided with a snap-in piece (50) thatwould be remove at the time the new plate is installed to ensure thatthe groove remains unfouled prior to surgery. In addition, as shown inFIGS. 3a to 3e , an optional window (52) can be provided in the platesystem to allow for the inspection of the disc space.

In addition to grooves that lock the sides of the plate and preventmovement of the arm perpendicular to the longitudinal axis of the plate,as used in the embodiments depicted in FIGS. 1 to 3, as shown in FIGS.4a to 4e , the linkage mechanism might also be provided with a mechanismfor resisting the movement of the plate along that longitudinal axis. Inthe embodiment shown in these figures both the channel (54) of the oldplate (55) and the arm (56) of the new plate (57) are provided withinterlocking ridges or teeth (58 & 59, respectively), such that when theplates are engaged (as shown in FIG. 4e ) the teeth in the channel ofthe old plate and the teeth on the arm of the new plate engage to lockthe arm into position along the longitudinal axis of the plates.

Although not shown, as discussed above, the channel within which the armof the new plate rests can also be provided with a snap-in piece thatwould be removed at the time the new plate is installed to ensure thatthe groove remains unfouled prior to surgery. In addition, as shown inthe figures, an optional window can be provided in the plate system toallow for the inspection of the disc space.

FIGS. 5a to 5f depict yet another possible embodiment of the basicdovetail slider plate system. In this embodiment, the new plate (60) isprovided with a pair of rails (62) rather than a central beam, each railhaving a groove (63) that would interlock with the groove (64) of thechannel (65) of the pre-installed plate (66). As shown in thecross-sectional views provided in FIGS. 5c and 5d , cooperative groovesboth operate together to provide a linkage that can only move in asingle dimension distally along the longitudinal axis of the originalplate thereby providing stability to and between the plates in all otherflexural directions. Again although only standard grooves are shown inthese embodiments, it should be understood that these linkages couldalso be provided with locking grooves to positively lock the arm of thenew plate into position within the trapezoidal channel of the old plate.

As with the embodiments shown in FIGS. 2 to 4, as shown in FIGS. 5e and5f , this groove and overlap mechanism allows the rails of the new plate(62) to snap into position and then to lock as it is pulled backward sothat it may be positioned from above and does not have to be fed inparallel to the previously placed plate (66). In addition to the grooveshown, because the rails can flex inwardly, an expansion fit could alsobe used such that once disposed within the groove the rails would expandoutwardly to press against the walls of the groove of the pre-installedplate. In such an embodiment, the rails could be made of a malleablemetal such as nytinol, which would allow for a dynamic expansion fit.

Although not shown in FIG. 5, once in position within the old plate anumber of mechanisms could be used to either exclusively or further lockthe rails into position, including, for example, a center lock screw(68, as shown in FIGS. 6a to 6e ), which could be placed between therails at a locking position (69) to lock the new plate into its desiredconfiguration. Other exemplary locking mechanisms include a top plate(not pictured) that would screw over the two plates, a slide lock groove(not pictured), or a block at the back of the rails (not pictured) thatwould prevent the rails from backing out of the groove of thepre-installed plate. All these locking mechanisms have the advantagethat they could be added after the new plate has been positioned, and donot need to be pre-installed on the old plate.

In addition, as shown in FIG. 6c , the channel (65) within which therails (62) of the new plate lock can also be provided with a snap-inpiece (70) that would cover the grooves (64) and locking position (69)on the pre-positioned plate prior to installation of the new plate toensure that the groove remains unfouled prior to surgery. In addition,as shown in the figures, an optional window (72) can be provided in theplate system to allow for the inspection of the disc space.

Although the interlocking mechanism of the coordinating surfaces on theembodiments discussed thus far (i.e., the grooves) have been situated onthe sides of the coordinating surfaces. In yet another embodiment, asshown in FIGS. 7a to 7f the interlocking mechanism is positioned alongthe faces of the coordinating surfaces. For example, as shown in FIGS.7a to 7c , in one embodiment, the pre-positioned plate has a groove (80)cut into the face of the coordinating channel surface (76), and the newplate (75) has a cooperative undercut (82) formed on the underside ofthe interlocking arm (78). As shown in FIGS. 7d to 7f , this overlappinggroove mechanism allows the arm (78) of the new plate (75) to snap intoposition from above and then to lock as it is pulled proximal to the newplate so that it may be positioned from above and does not have to befed in parallel to the previously placed plate (74).

Again, as discussed above, the interlocking grooves on the channel ofthe old plate and the arm of the new plate provide a linkage whenengaged that can only be moved in a single dimension distally along thelongitudinal axis of the original plate thereby providing stability toand between the plates in all other flexural directions. Although onlysimple groove profiles are shown in this embodiment, it should beunderstood that any groove profile suitable for interlocking the arm ofthe new plate with the old plate may be utilized. For example, a groovewith a locking barb may also be used, which would allow for a lockingsnap fit of the new plate. In addition, as shown in all of the figures,this plate may also be equipped with a window (83) for the inspection ofthe disc space.

Although the above-discussed plating systems have mechanisms designed toengage the inner surfaces of the plate, it should also be understoodthat the system of the current invention may also be designed to engagethe underside of the plate. One exemplary embodiment of such a systemshown in FIGS. 8a to 8d has an interlocking mechanism that takesadvantage of corrugations on the undersurface of a plate. As shown inFIG. 8a , as with many of the plates described above the systemgenerally includes a pre-positioned plate (300) that includes a channel(302) that can include a removable snap-in or removable blocker (304) onone or two ends of the plate. However, as FIG. 8b shows, in this system,the underside of the plate has an undercut (304) that includes aninterlocking indention (306). As shown in FIGS. 8c and 8d , when linkedwith a revision plate (308), the resilient arms of the cooperativeinterlocking mechanism (310) bend through the channel (302) and thenspring into position in the interlocking indentions (306) in theundercut (304) on the underside of the pre-positioned plate (300). Sucha system can provide an interlinking system for radically undercutplating systems, such as, for example, bendable plates that are too thinto allow further channeling in the top surface of the plate.

In addition, although all of the cooperatively interlockingconfigurations previously discussed involve the use of systems in whichthe attachment point between the pre-positioned plate and the new plateis internal to the plate, it should be understood that any suitableattachment mechanism may be used. For example, the embodiment of theinventive cervical plate system provided in FIGS. 9a to 9c , shows aplate system having a coupling groove on the external side of the plate.As shown in the figure, in this embodiment the two plates (84 and 85)have cooperative recesses (86 and 87) which engage each other to form anintegrated plate. As shown in FIG. 9c , when interlocked the two plateswould form a common passage (89) through which vertebral attachmentscrews (88) would be passed. Although not shown, such a system couldalso be provided with groove locks on the edges to the plate, such asthose discussed in relation to the other dovetail configurations toprovide further stability.

Because of the tight fit required for the operation of this embodimentof the invention, in addition, as shown in FIG. 9b , each of theinterlocking recesses that form the cooperative surfaces of the platingsystem would be provided with a snap-in piece (96) that would cover therecess prior to installation of the new plate to ensure that the grooveremains unfouled prior to surgery. In addition, although not shown inthe figures, an optional window could also be provided in the platesystem to allow for the inspection of the disc space.

Although the embodiment shown in FIG. 9 would require the removal andreplacement of the vertebral attachment during a revision surgery, itshould be understood that the current invention is also directed toexternal interlocking plate systems in which the vertebral attachmentscrews of the original plate may be left in place during revisionsurgery. Exemplary embodiments of such a cervical plating system areshown, for example, in FIGS. 10 to 16, which are discussed in greaterdetail below.

As shown in FIGS. 10a to 10c , similar to the embodiment of FIG. 9 thathas a partially external gripping portion, the two plates (1000 and1001) have cooperative recesses (1002 and 1003) which engage each otherto form an integrated plate. However, unlike the embodiment shown inFIG. 9c , where the interlocked plates would form a common passagethrough which vertebral attachment screws would pass, in the currentembodiment the original plate 1001 has three openings for screws withinits interlocking groove 1003. There are two recessed openings 1004through which vertebral attachment screws 1005 can pass, but it furtherhas a threaded opening 1006 into which a revision plate anchoring screw1007 would be inserted.

As shown in detail in FIGS. 10b and 10c , the interlocking groove 1003of the original plate 1001 is capped with a groove cover 1008 prior torevision. This snap-in cover protects the groove prior to installationof the new plate to ensure that the groove remains unfouled beforesurgery. Although the caps shown in FIGS. 10 to 16 all only provideprotection to the groove itself, it should be understood that the capcould be formed to mimic the externally gripping portion of the revisionoverlap, thereby providing additional protection to the lateral edge ofthe pre-positioned plate.

During revision surgery the cap 1008 is removed and the revision plate1000 is locked into the now exposed cooperating groove. Then the plateanchoring screw 1007 can be inserted through a hole 1009 in the top ofthe revision plate and into the cooperative threaded opening 1006 on theoriginal plate 1001. Using such a mechanism, allows for the attachmentof a revision plate via a single screw, and without the need to disturbthe vertebral attachment screws in the original plate.

As seen in FIGS. 10a to 10c , each revision plate has one end having aninterlocking undercut 1002, that allows for the interlocking attachmentwith the recessed groove 1003 of the original plate, and an opposite endthat has a interlocking upper recessed groove 1003′ identical to thegroove 1003 on the original plate that would allow for additionalrevision plates to be attached in serial in second, third or fourthlevel revision surgeries.

Although only one exemplary groove design has been discussed above, itshould be understood that any suitable interlocking groove geometrycould be employed in the current embodiment. For example, as shown inFIGS. 11a to 11c , the groove could include a more complicatedinterlocking surface, such as a chevron (or triangular section) 1010, oras shown in FIGS. 12a to 12c a curved surface 1011, to provideadditional stability.

One problem that is sometimes experienced during revision surgery occurswhen there is an axial misalignment between the longitudinal axis of theoriginal plate and that of the adjacent spine. In such a case, were arevision plate to be simply added in a straight line at the end of theoriginal plate it would be misaligned with the vertebra upon which it isto be anchored. In such cases it would be advantageous to be able toadjust, even slightly, the axis of the adjacent plate. In onealternative embodiment of the external gripping plate shown in FIGS. 9to 12, the interlocking grooves are designed with tolerances thatprovide for a small amount of rotation to allow for a radial adjustmentof the revision plate. Some exemplary embodiments of such a system areprovided in FIGS. 13a to 13 g.

As shown in FIGS. 13a and 13b , in one very basic form the interlockinggroove 1003 of the original plate 1001 is provided with a curve face1012 that allows for the interlocking face of the revision plate 1013 torock along its edge allowing for a radial angular adjustment 1014 thatserves to provide an adjustment to the longitudinal axis of the revisionplate 1000. As shown, this modification does not effect the overalldesign of the plate or the interlocking mechanism, it merely engineersan angular adjustment mechanism into such a plate.

Although the design in FIGS. 13a and 13b would provide a minimal amountof angular change, further revisions to the plates could enhance thiscapability. For example, as shown in FIGS. 13c and 13d , theinterlocking edge 1013 of the revision plate 1001 could be design tocooperate with the curved edge 1012 of the original plate. In such anembodiment, angular displacement of the revision plate could be achieved(as shown in FIG. 13d ) while providing enhanced interlocking stabilitybetween the plates. It should also be understood that although thegroove on each of these embodiments is provided with a convex shape, inthis interlocking design the curve could also be concave.

In addition, although only simple single hole interconnecting screwshave been shown thus far in the radially adjustable plate systems, itshould be understood that the extent of angular revision possible couldbe enhanced by allowing the plate anchoring screw 1007 to move in therevision plate hole 1009, such as by forming a slot 1014, as shown inFIGS. 13e and 13d , or by including several pre-positioned holes 1015within which the interlocking plate anchoring screw 1007 may be moved,as shown in FIG. 13 g.

Finally, although only single interlocking plate anchoring screws 1007have been shown thus far, it should be understood that any number anddisposition of screws may be used to attach the revision plate to theoriginal plate. For example, in FIGS. 14a to 14f a number of possiblegeometries for single and double interlocking anchoring screw designsare shown. In addition, although each of the embodiments shown in FIGS.14a to 14g describe interlocking plate anchoring screws that areseparate from the vertebral attachment screws 1004, in FIG. 15 anotherpossible embodiment is shown in which the threaded shafts 1006 for theplate anchoring screws 1007 are positioned inside the vertebralattachment screws 1005. In this embodiment it will be understood thatspecial vertebral attachment screws would need to be used in which thethreaded connections 1006 are formed into the shaft 1016 of thevertebral attachment screw itself.

Finally, although all of the embodiments of this externally interlockingplate have been shown with the interlocking plate anchoring screwsexposed, it should be understood that for extra protection these screwscould be covered with a separate snap-in cover 1017, as shown in FIGS.16a to 16c . Although not necessary, such a snap-in plate may furtherinclude a removal tool attachment point 1018, such as a slot forinsertion of a flat edge screw driver that would allow for the easyremoval of the cover when the interlocking plate anchor screw needs tobe accessed.

Although not shown, all such systems as shown in FIGS. 9 to 16 couldalso be provided with groove locks on the edges to the plate, such asthose discussed in relation to the other dovetail configurations toprovide further stability. In addition, although not shown in thefigures, an optional window could also be provided in the plate systemto allow for the inspection of the disc space.

Although only plating systems having interlocking mechanisms designedaround four screw plates have been discussed thus far, it should also beunderstood that other suitable designs can be contemplated in which thecooperative surfaces interlock around single hole plates. Although anumber of different embodiments are provided, the principal feature ofthe one-hole plating system is that the cooperative faces lock about asingle screw hole to anchor one end of the plates to the spine. Usingsuch a one-hole design allows for a low profile stackable add-on platingsystem.

Turning to the specific embodiments of the one-hole plating system,FIGS. 17a and 17b show an attachment system in which the new plate (90)is attached to the pre-positioned plate (92) via a stackable system inwhich a interlocking projection (94) on the new plate fits into acooperative recess (96) of the pre-positioned plate. As shown, onceinterlocked together, a single screw (98) is positioned through bothplates to lock them into place. Although the screw is necessary toattach the plates to the vertebra, the interlocking cooperative surfacesof the two plates provide additional stability by ensuring that theplates cannot slide in relation to one another when screwed intoposition.

In another configuration of a one-hole plate system, as shown in FIGS.18a to 18e , has an interlocking arrangement where the new plate (100)snaps around the outside edge of the pre-installed plate (102). In suchan embodiment, the coordinating surfaces of the plates may include arecessed arrangement as shown in FIGS. 18a and 18b , where the new platehas a recessed lip (104) upon which a cooperating edge of thepre-installed plate fits, or the pre-installed plate may be suppliedwith an external groove (106) to engage a cooperative groove (108)disposed on the inner edge of the new plate (100).

Finally, although the above one-hole plate system designs have allincorporated two identical one-hole plates. It should be understood thatthe new plate may be provided with additional vertebral securing meansto improve the lateral stability of the plate system. For example, inone embodiment shown in FIGS. 19a and 19b , the new revision plate (110)is “L” shaped and the projecting arm (112) is provided with a secondscrew hole (114) that allows for an additional stabilizing screw (116)to be inserted into the vertebral body. Although a right-handed “L” isshown in the diagram, it should be understood that the projecting armmay be disposed in either direction. Apart from this additionalstabilizing screw hole, the plates may interlock using any of thesystems described above.

In addition, although not shown in the figures, each of the interlockingrecesses and/or grooves that form the cooperative surfaces of theone-hole plating systems described above could be provided with asnap-in piece that would cover the recess/groove prior to installationof the new plate to ensure that the recess/groove remains unfouled priorto surgery. In addition, although not shown in the figures, an optionalwindow could also be provided in the plate system to allow for theinspection of the disc space.

Again, although a few specific embodiments of interlocking/revisableone-hole cervical plating systems are described above, it should beunderstood that a wide variety of one-hole plating systems may beincorporated with interlocking cooperative surfaces integrated thereinsuch that stable revision of the plates may be undertaken withoutnecessitating the removal of any pre-installed plates.

Although the above embodiments have all included plating systems inwhich the new plate interlocks within or around the body of thepre-installed plate, it should be understood that any suitable revisableplating system that provides a system of surfaces that cooperate toprovide a measure of stability independent from the anchoring screw maybe used in the current invention. For example, FIGS. 20 to 22 showvarious schematics of an embodiment of the invention in which the platesof the plating system are interlocked using a buttress fit. In thebuttress fit plating system only the leading edges (117) of the new andold plates interlock, as shown, for example, in FIG. 20c . In such anembodiment, a variety of grooves (FIGS. 20a to 20c , elements 117 a and117 b), or tabs (FIGS. 21a to 21c , elements 118 a and 118 b) orinterference fits (FIGS. 22a to 22c , elements 119 a and 119 b) could beused to interlock the plates. Such a system would allow the new plate tobe added on to the previously placed plate without a more involvedsystem of interlocking portions.

Such buttress fittings could be used as the sole means of interlockingthe plates, or they can be used in conjunction with one of theinterlocking systems described above. Where such a buttress fit is usedas the sole means of interlocking two plates an additional locking capor tab (120), as shown in FIGS. 21a to 21c ) may be included to provideadditional stability. Where such a buttress fit is used in conjunctionwith another interlock system, it can be used as a feature of the otherinterlocking system, can be an independent feature, or can be an add-onfeature, giving yet additional stabilizing support for the platingsystem.

Finally, although only systems having metal-on-metal or rigidinterlocking portions have been described thus far, it should be furtherunderstood that dynamic and flexible interlocking systems are alsocontemplated by the current invention. For example, FIGS. 23 and 24provide schematics of exemplary embodiments of plating systems that areinterlocked only through flexible bands or strands. As shown in FIGS.23a and 23b , in the simplest embodiment of such a system, a tensionband (122), which could be a metal or even polymer material, such as,for example braided Teflon or Surgistrand, would link two plates byattaching between connectors (124 & 126) on the new plate andpre-installed plate respectively. Alternatively, as shown in FIGS. 24aand 24 b, one could also use a metal or polymer connector (128) based onan interlocking system having ends (130) that would cooperate withgrooves (132) in the two plates. In either embodiment, an additionallocking mechanism, such as, for example, a screw, or a bar/rod with aratcheting mechanism, could be used to both fixedly attach the band andeven tension the band between the two plates if necessary. Although sucha flexible band would not be able to provide a rigid stabilizing effect,it would provide a dynamic tension that would stabilize the plate systemin all directions under stress.

Although the above discussion have focused on plating systems thatoperate by linking between the gaps in the vertebral anchors (e.g., thescrews) it should be understood that the same system of providing astable linkage without disturbing the fixation of the pre-positionedplate could be provided by overlapping one or more of the vertebralanchors of the pre-positioned plate. Exemplary embodiments of suchsystems are shown in FIGS. 25a to 25 d.

In one exemplary embodiment, as shown in FIGS. 25a to 25c , either thecooperative interlocking device, or armature (140) of the revision plate(142) could be contoured to wrap over the top of the screws (144) of thepre-positioned plate (146) and link with a channel (148) formed in bodyof the plate either by moving distally (FIG. 25a ) or proximally (FIG.25c ) into the channel (25 a and 25 c), or as shown in FIG. 25b thechannel (148) itself could be formed at an elevation higher than thescrews (144) allowing the armature (140) to slide into position over thetop of the screws. Alternatively, as shown in FIGS. 25d and 25e , inembodiments of plates with windows (150), the armature of thecooperative interlocking mechanism (152) could be designed to engage theedges (154) of the window thereby providing a locking mechanism withoutrequiring a significant spacing between the vertebral anchors (156) onthe pre-positioned plate (158). Finally, as shown in FIGS. 25f and 25g ,the armatures of the cooperative interlocking mechanism (160) of therevision plate (162) could be formed to engage the outer edges (168) ofthe pre-positioned plate (166) again providing a stabilizing mechanismwithout requiring a spacing between the vertebral anchors (156).

It should be understood that while certain channel/armature and grooveconfigurations are provided in the above-discussion, these are onlyprovided as examples, and any of the embodiments of linkage mechanismsprovided in this disclosure could be modified to engage over or aroundthe vertebral anchors instead of between them.

Finally, although specific locking mechanism have been discussed inrelation to a few of the plating systems described above, it should beunderstood that any of the plating systems could incorporate asupplementary locking mechanisms to further ensure the stability of theinterlock between the pre-installed plate and the new plate. Forexample, a covering plate that could be incorporate into any of thepreviously described plating systems could be designed to slide oraffixed over the interlocking portions of the plating system therebypreventing a disconnect between the two plates. Likewise an expansion orcrimped tab could be provided, which could be engaged over theinterlocking portion of the plating system after the plates have beenpositioned. In yet another embodiment, a rotating plate or bar could beplaced overlying the interlocking portion of the plating system. Indeed,it should be understood that these mechanisms are only exemplary, andany suitable mechanism that is capable of locking the interlockingportion of the plating system together may be used in the currentinvention.

An additional device for use with the new plating system is adistraction system. An exemplary embodiment of a distraction system isprovided in FIGS. 26a to 26d . In this embodiment, a distractor could beplaced on the pre-installed plate to distract off the plate. The currentmethod of distraction requires the placement of a distraction pin into avertebra below a disk space, and a second pin placed in the vertebraabove a disk space. These are long screws in pins that providesufficient purchase that a distracter can be placed overlying thesepins, and then a distraction force applied between the pins to open thedisk space. In the current invention, a single distraction pin (200)would be placed in the vertebra above or below the pre-installed plate(202), and then a mechanism (204) for hooking either a second pin (206)or the distractor (208) itself into the interlock mechanism of thepre-installed plate could be provided so that the plate would not needto be removed. Alternatively, as shown in FIG. 26d , the distractor(208) could be provided with an engaging element (210) that could bedirectly inserted between the vertebra to provide a stable face todistract the vertebra.

In either embodiment, once in place, this device could be used todistract off the previously placed plate. Alternatively, such a systemcould be used to place the plate system into compression. Either way,the distractor could be designed as a component of the modular platingsystem to allow for further revision flexibility without requiring theremoval or replacement of the pre-installed plate.

Regardless of the actual design, the features of the current platingsystem incorporate basic surgeon demands. These include ease of use, fewinstruments, flexibility, safety, and a sense of security for thesurgeon and patient. The additional stacking or modular plates can beincorporated to allow the new plate to settle, incorporating dynamism,or may be applied rigidly. Surgeons can choose these options during theoperation, either allowing screws to toggle in the plate, or for theplate to settle relative to the screws.

Although the above discussion has focused on the structure of theanterior cervical plating system of the current invention, it should beunderstood that the current invention is also directed to surgicalmethods using such a system. In addition, the system of the currentinvention can also be used with post-distraction systems, which can beaffixed to one vertebra and a plate, or to two plates. These instrumentscan also be used to compress constructs.

Moreover, although the plates shown in the above figures have beenexclusively directed to one level surgeries, it should be understoodthat the underlying structures are adaptable to two, three, and fourlevel neck surgeries as well. In addition, although only cervicalfusions have been discussed, the system of the current invention alsohas application in a variety of cervical spinal problems, includingdegenerative conditions, discectomy as well as corpectomy, deformity,trauma, tumor, and infection. Moreover, it is further possible to useany of the current cervical plating systems with an artificial discadded to an adjacent level, either as the primary or secondary surgery.In such an embodiment, this adjacent level may be joined by a similarcooperatively interlocking mechanism.

Although specific embodiments and exemplary embodiments are disclosedherein, it is expected that persons skilled in the art can and willdesign alternative cervical plating systems and methods of using suchsystems that are within the scope of the following claims eitherliterally or under the Doctrine of Equivalents.

What is claimed is:
 1. An anterior cervical plate comprising: arevisable cervical plate body having upper and lower horizontal faces,wherein at least a portion of the lower horizontal face is configured tobe disposed adjacent a first vertebral body; the revisable cervicalplate body defining at least one aperture configured to receive a firstvertebral anchoring mechanism to couple the revisable plate body to atleast the first vertebral body; the revisable cervical plate bodyfurther defining at least one interlocking receiver portion, at least apart of the interlocking receiver portion disposed below the upperhorizontal face, and configured to receive from above and form aninterconnection with a cooperative interlocking portion of a revisionplate; and wherein the at least one interlocking receiver portion isconfigured such that no threaded connector is attached thereto informing the interconnection.
 2. The plate of claim 1, wherein theinterlocking portion of the revisable cervical plate comprises a grooveformed into at least a portion of the upper horizontal face of the bodyof the revisable cervical plate.
 3. The plate of claim 2, wherein thegroove is configured to be cooperative with a portion of the revisionplate configured to overlap with the revisable cervical plate.
 4. Theplate of claim 1, wherein at least one of the vertebral anchoringmechanisms comprises a vertebral screw.
 5. The plate of claim 5, whereinthe at least one vertebral screw is positioned within the apertureformed in the revisable cervical plate body.
 6. The plate of claim 1,wherein the at least one interlocking portion is configured such that atleast a portion of the revision cervical plate overlaps at least oneaperture when interconnected with the revisable plate.
 7. The plate ofclaim 1, wherein at least the revisable cervical plate further comprisesan opening formed in the body of the revisable cervical plate disposedsuch that said opening overlaps and allows visual inspection of a discspace between two adjacent vertebra when said revisable cervical plateis anchored to a vertebral body.
 8. The plate of claim 7, wherein the atleast one interlocking portion includes at least one edge of theopening.
 9. The plate of claim 8, wherein the at least one edge of theopening further comprises a cooperative structure configured to engage acooperative projection on the revision cervical plate.
 10. The plate ofclaim 1, wherein the revisable cervical plate further comprises a secondinterlocking portion disposed opposite the interlocking portion.
 11. Theplate of claim 1, wherein the revisable cervical plate is adapted tospan at least two vertebral bodies, thereby stabilizing at least onelevel of the spine.
 12. The plate of claim 11, wherein the revisablecervical plate body is a single unitary piece.
 13. An anterior cervicalplate comprising: a revisable cervical plate having upper and lowerhorizontal faces, wherein at least a portion of the lower horizontalface is configured to be disposed adjacent at least a first vertebralbody, the at least one revisable cervical plate being adapted tostabilize at least one level of a spine; at least one interlockingreceiver portion defined by the revisable cervical plate body, whereinat least a portion of the upper horizontal face defines an entrance tothe interlocking receiver portion, the at least one interlockingreceiver portion configured to receive and form an interconnection witha portion of a revision cervical plate at least part of which overlapsat least a portion of the upper horizontal face of the revisablecervical plate body; and wherein the at least one interlocking receiverportion is configured such that no threaded connector is attachedthereto in forming the interconnection.
 14. The plate of claim 13,wherein the revisable cervical plate further comprises a groove alongits central longitudinal axis disposed such that a portion of therevision cervical plate is positioned within said groove when therevision and revisable cervical plates are interconnected.
 15. The plateof claim 13, wherein the revisable cervical plate is adapted to overlapat least two vertebral bodies.
 16. The plate of claim 13, wherein therevisable cervical plate body is a single unitary piece.
 17. The plateof claim 13, wherein when interconnected the revisable and revisioncervical plates are adapted to span the disc space between at least twovertebral bodies.
 18. The plate of claim 13, wherein the lowerhorizontal face is configured to be disposed adjacent at least twovertebral bodies.
 19. An anterior cervical plate comprising: a revisablecervical plate body having upper and lower horizontal faces, wherein atleast a portion of the lower horizontal face is configured to bedisposed adjacent a first vertebral body; at least a first vertebralanchoring mechanism configured to attach through the revisable platebody into at least the first vertebral body; an opening formed in thebody of the revisable cervical plate disposed such that said openingoverlaps and allows visual inspection of the disc space between twoadjacent vertebra when said revisable cervical plate is anchored to thefirst vertebral body; at least one interlocking portion disposed on therevisable cervical plate body comprising at least one edge of theopening and configured to be accessible from above the upper horizontalface of the revisable cervical plate body, the at least one Interlockingportion configured to form an interconnection with a revision cervicalplate Itself configured to overlap at least a portion of the upperhorizontal face of the revisable cervical plate body when the revisioncervical plate is disposed on a vertebral body adjacent the firstvertebral body; and wherein the at least one Interlocking portion isconfigured such that no threaded connector is attached thereto informing the interconnection.
 20. The plate of claim 19, wherein the atleast one edge of the opening further comprises a cooperative structureconfigured to engage a cooperative projection on the revision cervicalplate.